Parametric Study Research Articles

Experimental & numerical study on hybrid aluminium/GFRP thin-walled column under quasi-static axial loading

This paper discusses a research study to examine the behaviour of a circular thin-walled column subjected to quasi-static axial loading. Pure aluminium and hybrid aluminium/GFRP thin-walled column were experimentally tested, then a numerical simulation model using LS-Dyna approached the results. A parametric study was investigated with several material model parameters for a deeper understanding of the woven prepreg GFRP composite modelling. It was found that the failure mode and crashworthiness parameters result would be affected by parameter variations. Therefore, the values used for these parameters were obtained by doing parameter calibration so that the load-displacement response of the thin-walled column is similar to experimental results. The further parametric study result showed that the composite layers wrapped around the outer wall could increase the capacity of the energy absorption thin-walled column. Adding thickness to the composite layers would increase crashworthiness parameters, including mean crushing force, energy absorption, and specific energy absorption under quasi-static loading. Furthermore, the proposed modelling strategy developed in this work can be used as a reference for modelling the thin-walled column made of hybrid material due to the limited comprehensive numerical parametric studies on hybrid thin-walled column.

An acoustic black hole absorber for rail vibration suppression: Simulation and full-scale experiment

Rail vibration suppression is important to reduce rail noise radiation and ensure vehicle ride comfort. Conventional rail absorbers have been demonstrated to be effective for suppressing rail vibration; however, their effective frequency bandwidth remains limited. Herein, for the first time, we propose a broadband rail absorber, called an acoustic black hole (ABH) absorber, for rail vibration suppression. This novel ABH absorber consists of a variable-thickness cantilever beam with a power-law profile covered by a viscoelastic damping layer. A 3D finite element model of a 12.35-m long full-scale rail with ABH absorber was developed to investigate its performance. The effects of the thickness and loss factor of the damping layer on the rail vibration-suppression performance were investigated via a parametric study. In addition, a full-scale experiment was conducted on an actual rail to investigate the vibration-suppression performance of the ABH absorber. Both numerical and experimental results indicate that the ABH absorber can significantly reduce rail vibration at tuning frequencies and provide broadband vibration suppression within the non-resonance range. The experimental results demonstrate that the ABH absorber increases the track decay rate at frequencies above 100 Hz; in addition, a maximum track decay rate of 5.85 dB/m was achieved. This study may help to develop next-generation rail absorbers, which is important for developing sustainable and eco-friendly urban rail transit.

Wave-Induced Instantaneous Liquefaction of a Non-Cohesive Seabed around Buried Pipelines: A Liquefaction-Associated Non-Darcy Flow Model Approach

In complex marine environments, the wave-induced instantaneous liquefaction of the seabed is a key issue for the long-term safety control of marine structures. Existing computational frameworks for instantaneous liquefaction result in unreasonable tensile stresses in a non-cohesive seabed. To address this issue, a liquefaction-associated non-Darcy flow model has been proposed, but it has only been applied to the scenario of a pure seabed without a structure. In this study, we applied the previously proposed non-Darcy flow model to investigate the mechanism of wave–seabed–structure interactions under extreme wave loading considering a pipeline fully buried in a non-cohesive seabed. By comparing the liquefaction depths in the presence and absence of structures, it was found that the existence of structures weakens the attenuation of the pore pressure amplitude and influences the overall pore pressure distribution. Parametric studies were conducted. It was found that the liquefaction depth from the non-Darcy model is approximately 0.73 times that from the traditional Darcy model, regardless of whether or not a pipeline is involved. A quantitative relationship between the wave loading and structural size was established. The liquefied zone above the buried pipeline was found to be smaller than that in a pure seabed without a structure. A tentative explanation is provided for this phenomenon.

A computational tool for the design of rigid origami structures based on a lumped damage model

As it is well known, origami structures have broad application prospects in aerospace, medical, architectural, robotics, material science, and other engineering fields. However, the comprehension and modeling of the collapse process of this kind of structure are still in the process of development. This paper investigates one specific failure mode: ultra-low cycle fatigue under large displacements. Origami structures are represented as sets of elastic panels with small strains connected by inelastic (plastic-damaged) hinge lines with large rotations. A novel experimental study of the behavior of the Waterbomb origami structure subjected to cyclic loadings with constant amplitudes is first presented. Then, a new model of damage evolution for origami structures is proposed. Finally, parametric studies are described on the influence of several design parameters (initial folding height, number of sides of regular polygons, and length ratio) on structural collapse. The computational tools proposed in this paper can then be used for the optimum design of origami structures and the structural assessment during the two phases of loading: first, the deployment stage, and then service loads on the unfolded solid.

Axial live load distribution among single row of piles of integral bridges

This study investigates the axial live load distribution among steel H-piles in single-span integral bridges. To achieve this, two- and three-dimensional finite-element models for various integral bridges are conducted and analysed using the structural analysis software SAP2000, to determine the maximum axial loads in steel H-piles within two- and three-dimensional models. Subsequently, axial live load distribution factors from the ratio of axial loads calculated from these models are derived. The parametric study reveals that girder spacing and pile spacing exert notable influences on the axial live load distribution among the steel H-piles in integral bridges. Then, non-linear regression analysis is employed to formulate practical equations as functions of these two parameters. These equations can effectively calculate the live load distribution factors for the piles in integral bridges. To validate the accuracy of the live load distribution factors calculated from the proposed formulae, a comparative analysis is performed with results obtained from structural analysis. The standard deviations of the ratios between these two results are found to be a mere 2%. This clearly demonstrates that the developed formulae yield highly precise estimates of axial live load effects in integral bridge piles.

Quasi-Global Sensitivity Analysis of Supersonic Computational Fluid Dynamics Simulations

Determining the sensitivity of model outputs to input parameters is an important precursor to developing informative parameter studies, building surrogate models, and performing rigorous uncertainty quantification. Determining parameter sensitivities over a range of parameter values, termed global sensitivity analysis, requires many model evaluations sampled over the parameter space, which is intractable for many large-scale computational fluid dynamics (CFD) applications. For moderate parameter dimensions, we propose the use of Morris screening, a one-at-a-time quasi-global method for estimating parameter sensitivities over a range of parameter values for CFD simulations. The Morris method is implemented within a CFD framework that utilizes adaptive grid refinement, thereby enabling its application to state-of-the-art production-level problems. The method is shown to be viable for a model problem of supersonic flow over an axisymmetric capsule geometry with both physical and nonphysical (i.e., simulation-informing) input parameters. It is shown that Morris screening identifies relative parameter sensitivities consistent with those of more costly experimental and computational studies that were previously performed on this geometry.

Rock avalanche-induced air blasts: Implications for landslide risk assessments

Rock avalanche-induced air blasts are widespread, damaging, and deadly. They can add to the destructive potential of avalanches far beyond the avalanche zone, but no landslide risk assessment in practice to date has accounted for the potential air blast danger. Here, field investigations and numerical studies were employed to quantitively analyze the initiation and propagation mechanism of air blasts triggered by the 2008 Wenjia Valley rock avalanche in Sichuan, China. Our findings indicate that the most significant air blast triggered by the Wenjia Valley avalanche was near bends in the valley, with a maximum pressure of over 25 kPa and a maximum velocity of 73 m/s. The avalanche violently collided with the valley wall at bends, generating multiple destructive air blasts and avalanche deflection. Subsequently, the separated air blast propagated as inertia flows and caused huge forest destruction. A systematic parametric study combined with case studies was further performed to investigate the possible contribution of topography and sliding mass properties to the air blast power. Large avalanche volume and high velocity both appear to be necessary conditions to generate a destructive air blast, while the sudden topography change is also greatly influential. Our work provides new insights into the initiation and propagation of rock avalanche-induced air blasts, compelling to consider this sort of cascading effect during landslide risk assessment in mountainous regions.

Vibration isolation by relative resonance perceived in combination of rigid bodies and elastic beams

This paper develops a novel low-frequency vibration isolation device based on rigid body dynamics called a Rigid Elastic Vibration Isolator (REVI). The REVI model is realized by coupling four elastic beams with two rigid bodies monolithically made using 3D printing. The system operates based on the vibration of the intermediate rigid bodies, which leads to the anti-resonance phenomenon at low frequencies. The dynamic analysis of the proposed REVI system has been meticulously investigated through analytical methods and real-world experimentation. The analytical method uses the Spectral element method to obtain the dynamic response, which is also validated by the experimental findings. Furthermore, the REVI transmittance sensitivity analysis was conducted by adjusting the rigid mass and system load and exploring methods for generating wide low-frequency bandgaps. The inclination angle of the REVI system is also varied, revealing the bandgap characteristics regarding negative transmittance level. The parametric study varying the geometric properties of the REVI system enhances our understanding of the bandgap and attenuation characteristics within the attenuation band. The REVI mechanism is practical and easily implemented, allowing for accurate and repeatable modeling. Moreover, the analytical observations assist in refining the shape of the REVI mechanism to achieve the necessary bandgap for the desired transmittance.

Numerical modelling of the structural response of a novel hybrid densified wood filled-aluminium tube dowel for structural timber connections

This paper deals with the finite element modelling of the structural response of timber connections assembled using a novel hybrid dowel, made of densified wood filled aluminium tube, for the first time. Predictive and comprehensive finite element models, using the LS-Dyna Software, are developed to thoroughly investigate the non-linear 3D mechanical behaviour and optimize the design of the aluminium-to-timber connections. The materials parameters of the models are, first, identified based on experimental data from three-point bending tests. Then the models are validated by comparison to experimental data from slotted-in aluminium plate timber connections assembled either using steel dowel or hybrid densified wood filled aluminium tube dowel. The results are compared in terms of load-slip curves as well as in terms of failure modes. In addition, a parametrical study is conducted using the validated finite element model to investigate the influence of some material and geometrical parameters. The results showed that the hybrid densified wood filled aluminium tube dowels can be a potential substitute for conventional steel dowels. The study highlights the efficiency of the proposed finite element model in terms of quality of results and efficiency of use upstream the design process of such structures.

Hydrovoltaic electricity generator using a hierarchical NiFe LDH-coated CuO nanowire mesh device

Innovative advancements in sustainable water-energy nexus solutions are paramount in the current global context. This study introduces a hydrovoltaic electricity generator with advanced capillary wicking under ambient conditions. A hierarchical nanostructure of nickel–iron layered double hydroxides (NiFe LDHs) was deposited on copper oxide nanowires (CuO NWs) on Cu meshes to enhance the diffusion of ion-rich water. The LDH coating improves the overall power, voltage, and robustness of the device. A 200 µL droplet of hygroscopic solutions on a device produces electricity at 0.2 V scale, one of which could be sustained for over 140 h. We explored the working mechanisms, parametric studies, and potential scalability through serial allocation for further applications. This study allows water-driven electricity generation using hierarchical nanostructured materials, effectively harnessing renewable energy from readily available hygroscopic salts or abundant seawater resources.

An analytical vibration model of a one-dimensional two-stage periodic isolation system for the broadband vibration suppression of an underwater glider

Periodic isolation system is effectively applied in broadband vibration control. To further enhance the broadband vibration attenuation effect, the paper proposes a two-stage periodic isolation system for an underwater glider. The analytical model of the one-dimensional two-stage periodic isolation system is developed through the multi-degree of freedom spring mass model method. For illustrating the superiority of the proposed two-stage periodic isolator, the force transmission ratio and the wave propagation constant of the SDOF isolator, the single-stage periodic isolator, and the two-stage periodic isolator are calculated and compared. In order to obtain the dynamic parameter influences on the vibration isolation performances as the design guidelines of the two-stage periodic isolator, the parametrical study is carried out based on the analytical model. Furthermore, a two-stage periodic isolator is designed for an underwater glider. The application effect of the two-stage periodic isolator is investigated through analytical modeling and finite element method, comparing to the single-stage periodic isolator. The research results from the analytical models show the proposed two-stage periodic isolator could strength the broadband vibration suppression. The parametrical study results demonstrate the vibration attenuation bandgap and attenuation amount are greatly influenced by the designed dynamic parameters, such as the mass unit and the spring unit of the periodic isolator, the intermediate mass of the two-stage isolator, and the number of the periodic cells. In application study of an underwater glider, the finite element results verify that the two-stage periodic isolator has more vibration attenuation effect than the single-stage periodic isolator. The vibration isolation assessment according to the proposed analytical model gives good predictive performance before the finite element model verification.

Design of High-Frequency Carbon Nanotube-Carbon Nanotorus Oscillators for Energy Harvesting: A Molecular Dynamics Study.

The objective of this study is to examine the feasibility of using carbon-based nanostructures as nano-oscillators for future nanoelectromechanical applications such as energy harvesting devices and vibration sensing. The proposed nano-oscillator is comprised of a carbon nanotube (CNT) oscillating through a fixed carbon nanotorus molecule. For the first time in the literature, molecular dynamics (MD) simulations in conjunction with the Tersoff-Brenner (TB) and 6-12 Lennard-Jones (LJ) potential functions are adopted to determine the molecular interactions of the introduced nanodevice. To simulate the oscillatory behavior, two different schemes, namely, rigid and flexible, are considered. A detailed parametric study is performed to investigate the effects of rigidity, flexibility, and size of nanostructures as well as initial velocity on the force distribution and time histories of displacement and velocity of the core. Numerical results reveal that unlike the rigid oscillators, the flexible oscillators damp out within a few cycles. It is shown that the escape velocity of the flexible scheme is ∼6 times greater than that of the rigid scheme. The operating frequency and the generated power of rigid and flexible schemes under different system parameters are also calculated and compared. It is demonstrated that with increasing the ratio of nanotube-to-nanotorus diameter, the operating frequencies of both schemes decrease, while the generated powers do not behave monotonically. For a determined system parameter, it is observed that the flexible scheme provides higher operating frequencies compared to the rigid one. Moreover, considering that the initial velocity of the system is identical to the escape velocity, the generated power of the flexible scheme is calculated to be ∼14 times greater than that of the rigid scheme.

Comprehensive evaluation on the performance of a novel solar seawater desalination system

To address the scarcity of freshwater in isolated coastal areas without electricity, a novel solar seawater desalination system consisting of an efficient evacuated U-tube solar collector and hydrophilic modified tubular still is theoretically proposed. Based on the laws of thermodynamics, mathematical expressions for the freshwater yield rate, exergy efficiency and energy efficiency of the solar seawater desalination system are derived and used to predict the performance features. Under a solar irradiation intensity of 1000 W m−2, the freshwater yield rate, exergy efficiency and energy efficiency are, respectively, 2.75 kg m−2 h−1, 5.17 %, and 46.58 %, showing a bright prospect. To further enhance the performance, extensive parametric studies are conducted. Results indicate that increasing the working fluid flow rate, environment temperature, while decreasing the inlet water temperature of evacuated U-tube solar collector, wind velocity, as well as the hydrophilic modified tubular still tubular shell diameter and length, have a positive impact on the performance of solar seawater desalination system. Local sensitivity analyses further reveal that the wind velocity is the most sensitive variable, while the working fluid flow rate is the least sensitive variable. Based on the weather data from Ningbo, China, case studies reveal that, under realistic solar irradiation intensities of 964.25 W m−2 and 248.67 W m−2, the system demonstrates a freshwater yield rate, exergy efficiency, and energy efficiency of 2.62 kg m−2 h−1, 5.06 %, 46.18 %, and 0.45 kg m−2 h−1, 1.72 %, 31.21 %, respectively. Over a 21-year period (2002–2022), case studies demonstrate that the solar seawater desalination system can achieve an average annual freshwater yield rate of 1302.78 kg m−2.

Transverse Analysis of Box Girders with Corrugated Steel Webs

The utilisation of box girders with corrugated steel webs (CSWs) represents an innovative approach to bridge superstructure design that has garnered substantial popularity worldwide, with a notable prevalence in both Asia and Europe. Compared with traditional box girders, they avoid web cracking, improving the prestressing efficiency and bridge spanning ability. As an innovative box girder, a corrugated web can increase the cantilever length and transverse stiffness, and at the same time, it reduces the dead weight of the bridge deck. However, little research has been conducted on the mechanical properties of this novel spine-like box girder with CSWs, especially its transverse performance, although it has been used in many applications. In this paper, the effect of the web form on the behaviour of box girders is introduced. Therefore, three representative three-dimensional (3D) finite-element models (i.e., corrugated web box girder, flat web box girder, and ordinary equivalent concrete web box girder) have been established to quantitatively investigate the influence of corrugated web stiffness on transverse stress under the action of gravity and vehicle loads. Generally, significant differences in the mechanical performance of box girders with CSWs have been observed compared with conventional box girders with concrete webs. Additionally, parametric studies to investigate the influences of the corrugation dimensions (in term of the corrugation height, web thickness, panel width, web height and elastic modulus) on the transverse stiffness of such bridges are analyzed. The results show that a new stiffness formula can be put forward to consider the effect of web height, and a high-strength steel web needs to be developed urgently for box girders with CSWs in the near future. Overall, the results of this investigation can be used as a reference for transverse designing and segmental construction of similar projects.

Dynamical behavior of a spinning tapered Rayleigh beam subjected to an axial load

As a first attempt, the vibration and stability analysis of a spinning tapered beam subjected to an axial load are investigated. The radius of the cross-section of the beam is assumed to vary exponentially in the longitudinal direction. The tapered beam is modeled in Rayleigh beam assumption with rotary inertia, eccentricity, and gyroscopic effects. Based on the Hamilton principle, the governing equations of motion of the spinning tapered beam with an axial force are obtained. Also, a Galerkin discretization scheme is employed to obtain the natural frequency and critical divergence rotating speeds of the system. As a result, the instability thresholds and stability evolution of the system are acquired. Furthermore, a detailed parametric study is conducted to evaluate the effects of the slenderness ratio, taper parameter, axial load, and eccentricity ratio on the dynamical behavior of the system. The results show that the natural frequency and critical divergence rotating speed of the tapered beam are larger than those of the circular-section beam. In addition, the axial load, taper parameter, and eccentricity are the key factors that influence the stability of the system.

A parametric study on patch repaired quasi‐isotropic laminate in high‐velocity impact environment: Experimental and numerical investigation

AbstractIn this work, the post‐repair behavior of a quasi‐isotropic laminate was studied in a high‐velocity impact environment. The composite laminates were repaired using an external bonded patch repair procedure. Impact tests were performed to understand the effect of patch size and the result of filling the damaged region with a neat epoxy and hardener mixture. Two different size square patches, such as 30 and 50 mm, were used to analyze the effect of patch size. A continuum damage mechanics‐based model was developed and incorporated into a finite element model interface to estimate the optimum patch size and patch stacking sequence for the impact environment. In the finite element model, the intralaminar failure criteria were implemented using the ABAQUS‐VUMAT user subroutine, and the interlaminar failure criteria were implemented using the inbuilt cohesive contact properties. The 30 mm patch with resin filled in the damaged region performed better than the other combination patches. Also, placing 45° plies toward the outer layer of the patches showed lower damage compared to the patches in which 45° plies were placed at the inner surfaces.Highlights Post‐repair impact behavior of repaired laminates was examined. Impact of patch dimension and resin filling in the damaged area was analyzed. A 3‐D finite element model was developed to optimize patch parameters. Continuum damage mechanics model has been incorporated with VUMAT subroutine. Interface between lamina has been modeled using cohesive contact.

Evaluation of the structural performance of T-section beams with construction defects utilizing numerical analysis

This study investigates recent incidents of slabs collapse in reinforced concrete T-beam constructions attributed to deficiencies in design detailing and execution. It employs numerical analyses using the finite element method in ANSYS software to model T-section beams, with validation against experimental tests. Subsequently, a parametric study is conducted to explore the behavior of T-section beams under various design and construction variables, including the spacing of secondary reinforcements in the slab, the diameter of secondary main reinforcements, and slab thickness. The numerical analysis results are found to align well with experimental findings. The parametric study highlights that the eccentricity of reinforcing bars in the secondary direction of the slab is more detrimental than in the main direction. Furthermore, using 10 mm diameter reinforcement in the slab, either in the main or secondary direction, enhances the slab’s resistance to applied loads. Additionally, the study reveals that increasing the stiffness of the slab contributes to an improved resistance of the beam.

Effects of Pipe Deflection and Arching on Stress Distribution and Lateral Earth Pressure Coefficient in Buried Flexible Pipes

In this study, full-scale laboratory tests were conducted on a 315 mm diameter HDPE pipe under shallow buried and localised surface loading conditions to investigate the effects of pipe deflection and arching on stress distribution and the lateral earth pressure coefficient. The tests were validated using 2D finite element software, and further analyses were carried out through parametric studies. These studies considered variations in pipe stiffness, burial depth, backfill properties and pavement stiffness to increase the reliability of the test results. For a shallowly buried HDPE pipe, a comprehensive explanation is provided regarding the evolution of the lateral earth pressure coefficient within the central soil prism. Initially set at Ko conditions, this coefficient tends to shift towards Kp with increasing arching and transitions to Ka with weakening arching. The findings suggest that stress predictions in the crown region of shallow buried flexible pipes are achievable through the application of Terzaghi’s arching theory, contingent upon an accurate estimation of the lateral earth pressure coefficient for the central soil prism. Furthermore, the horizontal deflection of the pipe at the springline results in compressive behaviour and passive effects in the surrounding backfill in this specific region. This situation demonstrates that the horizontal stresses at the springline and the lateral earth pressure coefficient can be reliably estimated by considering them as functions of the horizontal deflection of the pipe.

Seismic Response of RCC Buildings on Hill Slopes with Step Back and Step Back - Set Back Configuration

Framed structures constructed on hill slopes have different structural behavior than those on flat ground due to the scarcity of flat land. As these buildings are unsymmetrical, they attract large amounts of shear forces and torsional moments, leading to unequal distribution due to varying column lengths. In this study, the dynamic response of hill buildings has been compared with step back and step back set back building without and with bracing at corner of the building in terms of maximum storey stiffness and storey displacement. Two different types of buildings have been modeled and analyzed using ETABS v 18.0 finite element code. A parametric study has been conducted, in which hill buildings are geometrically varied in height of the structure due to hill slope. All sixteen analytical models have been subjected to seismic forces along and across the hill slope direction and analyzed by using the Response Spectrum Method.
 All 16 models were analysed using ETABS v18. Three dimensional space frame analysis is carried out for four different configurations such as step back buildings with bracings at corner of the building, step back buildings without bracings, step back and set back building with bracings at corner of the building, step back and set back building without bracings. The maximum storey stiffness and storey displacement for the step back and step back-setback buildings with and without bracing are at 15 ͦ and 30 ͦ, respectively, compare with bracing buildings, the value in step back & step back set back building drastically decreases, resulting in the stability of the building.

Preparation of Samples for the Study of Rheological Parameters of Digested Pulps in a Bioreactor of an Agricultural Biogas Plant

The studies of the rheology of digested pulp from agricultural biogas plants have often been fragmentary and non-standardised due to their complexity and time-consuming nature. As a result of measurements, it was possible to develop a procedure and range of measurements for the correct determination of the parameters of the carrier substance. The applicability of the coaxial cylinder measurement system was demonstrated for assessing the rheological parameters of digested pulp from a fermenter that utilises agricultural biomass. To determine the characteristics of solid particles, the Zingg diagram was used, inter alia, allowing the comparison of particles from each fraction. The analysis of the shape and size of solid particles may help to describe the onset of motion of this phase, flow type, or sedimentation type. The authors propose a completely new research approach to obtain an appropriate, repeatable test conditions of medium, which is the carrier liquid from the biogas plant reactor. The proposed methodology and the scenario of the entire study make it possible to achieve scalable and comparable test results in any laboratory. The proposed solution eliminates the influence of most external factors on the sample and rheological measurements, and the effectiveness of the presented procedure was confirmed in tests.